Lactic acid bacteria are the bacteria metabolizing carbohydrate and producing lactic acid thereby. These bacteria belong to facultative anaerobes or obligatory anaerobes which proliferate well under anaerobic conditions. Lactic acid bacteria are divided into 5 genuses, which are Streptococcus, Lactobacillus, Leuconostoc, Bifidobacteria and Pediococcus. A Streptococcus genus microorganism is a homofermentive bacterium that generates lactic acid by fermenting milk to suppress putrefying bacteria or pathogenic bacteria. A Lactobacillus genus microorganism is a bacilliform, and a homo- or heterofermentive bacterium, which is widely seen in the fermentation of dairy products or vegetables. A Leuconostoc genus microorganism, a diplococcus, is a heterofermentive bacterium and mostly involved in fermenting vegetables. A Bifidobacteria genus microorganism is an obligatory anaerobe which generates L(+) lactic acid useful for children's health, but cannot survive under aerobic conditions. Lastly, a Pediococcus genus microorganism is a homofermentive bacterium having the form of tetracoccus, which is mostly found in Kimchi or brined foods and involved in the fermentation of meats including sausages. Among them, Bifidobacteria are the major obligatory anaerobic lactic acid bacteria found in human intestines, and they are counted 100–1000 times as many as facultative anaerobic lactic acid bacteria such as Lactobacillus and Streptococcus in human intestine.
Lactic acid bacteria control pH of intestines to keep them acidic condition, so that they inhibit the proliferation of harmful bacteria like E. coli or Clostridium sp. And they moderate diarrhea and constipation, and play an important role in vitamin synthesis, anticancer activity, lowering serum cholesterol and the like. Particularly, lactic acid bacteria have a specific protein that can be adhered tightly to mucosa and epithelial cells of intestines, to have an intestinal function-controlling effect inhibiting the growth of harmful bacteria. In addition, lactic acid bacteria stimulate the proliferation of macrophages, resulting in the enhancement of the capability of macrophage to recognize and sterilize harmful bacteria invaded in intestines. They, further, stimulate the secretion of immune-related substances, resulting in the enhancement of the immunity (Gabriela perdigon et al., J. of food Protection 53:404–410, 1990; Katsumasa sato et al., Microbiol. Immunol., 32(7):689–698, 1988). Especially, Lactobacillus genus microorganism produces acidophillin to inhibit the growth of harmful bacteria such as dysentery bacillus (Shigella), salmonella and staphylococcus, and the proliferation of causal bacteria of diarrhea, resulting in the normalization of intestinal flora and the cease of diarrhea. In addition, Pediococcus pentosaceus has been confirmed to have an excellent ability to inhibit the growth of harmful bacteria such as Helicobacter pylori, Listeria sp. and the like by secreting a strain specific antibacterial peptide.
Recently, studies have actively been progressing about separating lactic acid bacteria and developing a live bacterial medicine, food additive and intestinal function-controlling agent using the same, in order to keep minor lactic acid bacteria inhabiting human intestines longer. Korean patent No.264295 discloses “Novel Bifidobacterium longum MK-G7 bifidus strain having a physiological activity suitable to Koreans and a use thereof”, and Korean patent No.158049 discloses “Bifidobacterium longum HS90 producing mucopolysaccharide having an excellent humidness”. Also, Korean patent No.2000-316517 discloses “Novel Lactobacillus acidophilus YD9904 strain having an excellent acid producing ability and acid resistance, and a product containing the same”, and the Korean patent No.2001-70689 discloses “Lactobacillus acidophilus 30SC having a great acid resistance and bile-tolerant activity as well as an antibacterial activity of inhibiting the growth of pathogenic bacteria and putrefying bacteria”. Korean patent No.2001-11797 discloses “Novel acid-tolerant Lactobacillus luteri probio-16 having an antimicrobial activity against rotavirus and harmful microorganism, and live bacterial activator containing the same”. That is, almost all the studies about lactic acid bacteria have been focused on Lactobacillus genus microorganisms and Bifidobacterium genus microorganisms having an acid-tolerant and/or an anti-microbial activity.